In this Oct. 26, 2017, file photo, New Zealand Prime Minister Jacinda Ardern, center left, embraces her partner Clarke Gayford after speaking to well-wishers in front of the parliament in Wellington, New Zealand. Ardern announced on Friday, Jan. 19, 2018 that she expecting her first child in June. AP Photo/Nick Perry.

Big question about Ardern's pregnancy

THIS morning news broke that New Zealand Prime Minister Jacinda Ardern is expecting her first child. This is huge news for the country, and indeed for the world.

Arden will be only the second modern head of government to give birth while in office, after Benazir Bhutto, Prime Minister of Pakistan, gave birth to her third child in 1990.

This is a both a significant moment in history, and a completely mundane one.

Arden's news is significant because it highlights the shifting paradigm of gender roles in child rearing. Arden has announced that her television presenter husband, Clarke Gayford, will be 'primary caregiver' for their child when she returns to work after six weeks of maternity leave.

And stay-at-home dads are far more visible now than 10 years ago, helped along by celebrity dads like Brad Pitt and David Beckham, and blogs such as Dad or Alive and Australia's Reservoir Dad.

In reality, however, the number of dads taking on primary responsibility for their babies and children remains depressingly low. A recent Australian Government study showed that the number of stay at home dads in two-parent, opposite sex families had barely risen above 4 per cent since 2011.

I don't believe Ardern and Gayford are making a deliberate political statement. They are simply a working couple having a baby, who have decided that the father's career is more readily put on hold to care for the infant. While Gayford, too, has a high-profile career, it's hard to argue with the fact that running the country is rather more significant.

But, given the low numbers of couples making a similar choice, their example will be hugely important. Both working women and their male partners need to see that it is a viable option for men to take on responsibility for the kids while their partners stay in the workforce.

On the other hand, Ardern's pregnancy should be utterly mundane news. Politicians - even world leaders - have babies all the time. British Prime Minister David Cameron had a new baby while he was in office, as did his recent predecessor Tony Blair.

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A look at the background of NZ Prime Minister.

Australians Bill Shorten, Joe Hockey, Christopher Pyne and Josh Frydenberg have all had babies while serving as ministers. So what on earth is the big deal?

Well, the big deal, of course, is that they are men, and have wives at home to care for the kids. No-one worried about the impact of a newborn on Cameron or Shorten or Frydenberg, because they had their partners to deal with all the night feeds and nappies.

So why on earth can't a male partner do the same? Why should a newborn impact on a woman more than a man? Pregnancy isn't a disease, and a pregnant woman can work right until giving birth.

And once the baby has been born, and the woman is up and about again, there is absolutely no reason why the dad can't step up and take on the bulk of the child rearing.

Let's celebrate this news because every new baby is worth celebrating. Let it inspire more fathers to be stay-at-home parents, so that more women can stay in the workforce, and so that dads can experience all the joys that child raising has to offer.

And let's hope that soon, this won't even be noteworthy. A working parent and a stay-at-home parent make an excellent combination, and it shouldn't matter which one is the mum or the dad.